# PyPy[oz-thread-api]

PyPy[oz-thread-api]
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# Some rough notes about the Oz threading model

(almost verbatim from CTM)

# Scheduling

Fair scheduling through round-robin.

With priority levels : three queues exist, which manage high, medium, low priority threads. The time slice ratio for these is 100:10:1. Threads inherit the priority of their parent.

Mozart uses an external timer approach to implement thread preemption.

# Thread ops

All these ops are defined in a Thread namespace/module.

this() -> current thread's name (not another thread's name) state(t) -> return state of t in {runnable, blocked, terminated} suspend(t) : suspend t resume(t) : resume execution of t preempt(t) : preempt t terminate(t) : terminate t immediately injectException(t, e) : raise exception e in t setPriority(t, p) : set t's priority to p

Interestingly, coroutines can be build upon this thread API. Coroutines have two ops : spawn and resume.

spawn(p) -> creates a coroutine with procedure p, returns pid resume(c) : transfers control from current coroutine to c

The implementation of these ops in terms of the threads API is as follows :

def spawn(p):
  in_thread:
    pid = Thread.this() Thread.suspend(pid) p()
def resume(cid):
  Thread.resume cid Thread.suspend(Thread.this())